Tonometer- and ultrasound-based pulse wave analysis – a comparative study

Background and Objective Arterial pulse wave analysis (PWA), a tool capable of reflecting regional hemodynamics and wave propagation characteristics, has been primarily based on tonometric measurements, while ultrasound has been used for evaluating local arterial wall mechanics. This study investigates the accuracy of aortic PWA, derived from ultrasound measurements of carotid diameter, in comparison to standard tonometry. Methods A sub-dataset of the FUCHSIA study (i.e., patients with fibromuscular dysplasia, matched hypertensives and matched healthy controls) with pairs of carotid ultrasound (MyLab, ESAOTE, Genoa, Italy) and tonometric (SphygmoCor CvMS, Atcor Medical) recordings were used for analyses. Ultrasound longitudinal scans were processed as follows: extraction of diameter curves (Carotid Studio, Quipu); discarding low-quality curves; transformation of diameter to local pressure curves by mathematical models; machine-learning-based transformation from carotid to aortic pulse waves; and finally, calibration of aortic pressure curves. ARCSolver algorithms (AIT) were applied to these ultrasound-based aortic pressure waveforms and the tonometry-based aortic waveforms as reference method to derive PWA parameters (e.g., heart rate (HR), central systolic pressure (cSBP) and augmentation index (AIx)) for pairwise comparison. Results In total, 74 recordings from 49 patients (51 (SD 15) years; 15 men) were used in this comparative study. Tonometry- and ultrasound-derived HR correlated well (r=0.88) with no significant bias (mean difference 0.58 (SD 4.9) bpm). Comparable results were obtained for cSBP (r=0.97, mean difference -3.6 (SD 4.2) mmHg) and AIx (r=0.77, mean difference -4.2 (SD 9.1) %). Conclusions Central PWA parameters obtained from carotid ultrasound-derived aortic pressure curves showed agreement with tonometry-based measurements and results are in line with literature.